As a power source to be used in various mobile devices such as a mobile telephone and a notebook personal computer, a lithium ion secondary battery which is a high energy density non-aqueous secondary battery has been used. The lithium ion secondary battery mainly comprises a cylindrical shape or a rectangular shape, and in most cases, is formed by inserting a wound electrode laminate into a metallic can. Depending on the kind of mobile device, the thickness of the battery is requested to be thin. However, the metallic can formed by deep drawing processing is difficult to have a thickness of 3 mm or less, and hence it is difficult to set the thickness of a secondary battery using a metallic can to 3 mm or less.
On the other hand, in recent years, various types of IC cards and non-contact IC cards have been spread, and most of the non-contact IC cards are designed in such a manner that electric power is generated by an electromagnetic induction coil, and an electric circuit is operated only during use. In order to provide these IC cards with a display function or a sensing function so as to greatly enhance the security and convenience, it is desired that a secondary battery serving as an energy source be built in each IC card. The size of each IC card is standardized to, for example, 85 mm×48 mm×0.76 mm, and hence the thickness of a secondary battery to be built in the IC card is required to be 0.76 mm or less. Further, even in various card-type devices which do not comply with the specification, it is preferred that the thickness of a secondary battery be 2.5 mm or less. Therefore, it is difficult to use the above-mentioned secondary battery using a metallic can.
As a thin non-aqueous secondary battery having a thickness of 2.5 mm or less, there is given a non-aqueous secondary battery including an aluminum laminate film on an exterior body. The aluminum laminate film includes mainly a thermoplastic resin layer, an aluminum foil layer, and an insulating layer, and has a feature of being able to be molded and processed easily while having a sufficient gas barrier property. However, in the case of the thin non-aqueous secondary battery, the proportion of the exterior body occupying the thickness of the entire battery is high, and hence a technology for making the exterior body as thin as possible is required in order to enhance energy density.
Patent Literature 1 discloses an aluminum laminate film with a 7-layer structure including an innermost layer, a first adhesive layer, a first surface treatment layer, an aluminum foil layer, a second surface treatment layer, a second adhesive layer, and an outermost layer, and having excellent moldability, gas barrier property, heat sealing property, and electrolytic solution resistance (Patent Literature 1).
Patent Literature 2 proposes a thin battery which does not require an aluminum laminate by allowing a positive-electrode collector and a negative-electrode collector to serve as an exterior body. In this battery, peripheral edges of the positive-electrode collector and the negative-electrode collector are joined with a sealing agent containing polyolefin or engineering plastic (Patent Literature 2).
Patent Literature 3 also proposes a thin battery which does not require an aluminum laminate by allowing a positive-electrode collector and a negative-electrode collector to serve as an exterior body. This literature proposes that peripheral edges of the positive-electrode collector and the negative-electrode collector are joined with an olefin-based hot melt resin, a urethane-based reaction-type hot melt resin, an ethylene vinyl alcohol based hot melt resin, a polyamide-based hot melt resin, or the like, and these hot melt resins are filled with an inorganic filler (Patent Literature 3).
Further, Patent Literature 4 discloses a structure of an electric double-layer capacitor in which an electrolyte is sandwiched between a positive-electrode collector containing aluminum and a negative-electrode collector similarly containing aluminum, and a gap is filled with a multilayer structure comprising a welded layer and a gas barrier layer (Patent Literature 4). That is, Patent Literature 4 discloses an electric double-layer capacitor in which the positive-electrode collector and the negative-electrode collector are formed of the same aluminum.